Factor using the ac-method.
-$21 - 10 x + x ^ { 2 }$
A) $( x + 3 ) ( x - 7 )$
B) $( x + 3 ) ( x + 7 )$
C) $( x - 3 ) ( x - 7 )$
D) $( x - 3 ) ( x + 7 )$

Question

Quizplus · Accepted Answer

The correct factorization of $21 - 10x + x^2$ is $(x - 3)(x - 7)$. This is found by looking for two numbers that multiply to $21$ (the product of the coefficient of $x^2$ and the constant term) and add to $-10$ (the coefficient of $x$). The numbers $-3$ and $-7$ satisfy these conditions.

Factor Using the Ac-Method 21−10x+x221 - 10 x + x ^ { 2 }21−10x+x2

Factor Using the Ac-Method $21 - 10 x + x ^ { 2 }$